Kidney organoids reveal redundancy in viral entry pathways during ACE2-dependent SARS-CoV-2 infection

With a high incidence of acute kidney injury among hospitalized COVID-19 patients, considerable attention has been focussed on whether SARS-CoV-2 specifically targets kidney cells to directly impact renal function, or whether renal damage is primarily an indirect outcome. To date, several studies have utilized kidney organoids to understand the pathogenesis of COVID-19, revealing the ability for SARS-CoV-2 to predominantly infect cells of the proximal tubule (PT), with reduced infectivity following administration of soluble ACE2. However, the immaturity of standard human kidney organoids represents a significant hurdle, leaving the preferred SARS-CoV-2 processing pathway, existence of alternate viral receptors, and the effect of common hypertensive medications on the expression of ACE2 in the context of SARS-CoV-2 exposure incompletely understood. Utilizing a novel kidney organoid model with enhanced PT maturity, genetic- and drug-mediated inhibition of viral entry and processing factors confirmed the requirement for ACE2 for SARS-CoV-2 entry but showed that the virus can utilize dual viral spike protein processing pathways downstream of ACE2 receptor binding. These include TMPRSS- and CTSL/CTSB-mediated non-endosomal and endocytic pathways, with TMPRSS10 likely playing a more significant role in the non-endosomal pathway in renal cells than TMPRSS2. Finally, treatment with the antihypertensive ACE inhibitor, lisinopril, showed negligible impact on receptor expression or susceptibility of renal cells to infection. This study represents the first in-depth characterization of viral entry in stem cell-derived human kidney organoids with enhanced PTs, providing deeper insight into the renal implications of the ongoing COVID-19 pandemic.

IMPORTANCE

Utilizing a human iPSC-derived kidney organoid model with improved proximal tubule (PT) maturity, we identified the mechanism of SARS-CoV-2 entry in renal cells, confirming ACE2 as the sole receptor and revealing redundancy in downstream cell surface TMPRSS- and endocytic Cathepsin-mediated pathways. In addition, these data address the implications of SARS-CoV-2 exposure in the setting of the commonly prescribed ACE-inhibitor, lisinopril, confirming its negligible impact on infection of kidney cells. Taken together, these results provide valuable insight into the mechanism of viral infection in the human kidney.

L-arginine and lisinopril supplementation protects against sodium fluoride-induced nephrotoxicity and hypertension by suppressing mineralocorticoid receptor and angiotensin-converting enzyme 3 activity

Sodium fluoride (NaF) is one of the neglected environmental toxicants that has continued to silently cause toxicity to both humans and animals. NaF is universally present in water, soil, and atmosphere. The persistent and alarming rate of increase in cardiovascular and renal diseases caused by chemicals such as NaF in mammalian tissues has led to the use of various drugs for the treatment of these diseases. The present study aimed at evaluating the renoprotective and antihypertensive effects of L-arginine against NaF-induced nephrotoxicity. Thirty male Wistar rats (150-180 g) were used in this study. The rats were randomly divided into five groups of six rats each as follows: Control, NaF (300 ppm), NaF + L-arginine (100 mg/kg), NaF + L-arginine (200 mg/kg), and NaF + lisinopril (10 mg/kg). Histopathological examination and immunohistochemistry of renal angiotensin-converting enzyme (ACE) and mineralocorticoid receptor (MCR) were performed. Markers of renal damage, oxidative stress, antioxidant defense system, and blood pressure parameters were determined. L-arginine and lisinopril significantly (P < 0.05) ameliorated the hypertensive effects of NaF. The systolic, diastolic, and mean arterial blood pressure of the treated groups were significantly (P < 0.05) reduced compared with the hypertensive group. This finding was concurrent with significantly increased serum bioavailability of nitric oxide in the hypertensive rats treated with L-arginine and lisinopril. Also, there was a significant reduction in the level of blood urea nitrogen and creatinine of hypertensive rats treated with L-arginine and lisinopril. There was a significant (P < 0.05) reduction in markers of oxidative stress such as malondialdehyde and protein carbonyl and concurrent increase in the levels of antioxidant enzymes in the kidney of hypertensive rats treated with L-arginine and lisinopril. The results of this study suggest that L-arginine and lisinopril normalized blood pressure, reduced oxidative stress, and the expression of renal ACE and mineralocorticoid receptor, and improved nitric oxide production. Thus, L-arginine holds promise as a potential therapy against hypertension and renal damage.

Predicting response to lisinopril in treating hypertension: a pilot study

INTRODUCTION

Only ~ 50% of hypertensive patients will respond to treatment.

OBJECTIVE

This pilot study aims to identify clinical and metabolite markers that predict response to lisinopril.

METHODS

Hypertensive patients (n = 45) received lisinopril (10 mg) at their baseline visit. Blood pressures were reevaluated one week later. Responders to lisinopril (n = 19) were defined by a 10% decline in systolic blood pressure. Plasma metabolites were evaluated with mass spectrometry.

RESULTS

BMI (p = 0.009), GFR (p = 0.015) and 2-oxoglutarate were included in a logistic regression model to predict response to lisinopril.

CONCLUSIONS

Further validation cohorts are needed to confirm the predictive values of these clinical and metabolic markers.

[Effect of angiotensin converting enzyme lisinopril on the state of vascular bed in premenopausal women with arterial hypertension]

We assessed effect of lisinopril on structural-functional state of vascular bed in 82 premenopausal women with hypoestrogenia and arterial hypertension (AH). Test with postocclusion reactive hyperemia showed that at the background of significant lowering of endothelial vasomotor function before treatment 47.5% of women had inertial type of vasomotor reaction. This evidenced for considerable role of dyshormonal states in progression of AH first of all at the account of increase of vascular stiffness and development of endothelial dysfunction. Lisinopril improved structural-functional state of vascular wall of common carotid arteries, affected positively dysfunction of endothelium, lowered stiffness of arterial vascular wall.

Construction, identification and application of HeLa cells stably transfected with human PEPT1 and PEPT2

The purpose of this study was to construct stably transfected HeLa cells with human peptide transporters (hPEPT1/hPEPT2) and to identify the function of the transfected cells using the substrate JBP485 (a dipeptide) and a typical substrate for PEPTs, glycylsarcosine (Gly-Sar). An efficient and rapid method was established for the preparation and transformation of competent cells of Escherichia coli. After extraction and purification, hPEPT1/hPEPT2-pcDNA3 was transfected into HeLa cells by the liposome transfection method, respectively. HeLa-hPEPT1/hPEPT2 cells were selected by measuring the protein expression and the uptake activities of JBP485 and Gly-Sar. A simple and rapid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the simultaneous determination of JBP485 and Gly-Sar in biological samples. The Michaelis-Menten constant (K(m)) values of Gly-Sar uptake by the hPEPT1 and hPEPT2-expressing transfectants were 1.03 mM and 0.0965 mM, respectively, and the K(m) values of JBP485 uptake were 1.33 mM for PEPT1 and 0.144 mM for PEPT2. The uptake of Gly-Sar was significantly inhibited by JBP485 with a K(i) value of 8.11 mM (for PEPT1) and 1.05 mM (for PEPT2). Maximal uptake of Gly-Sar were detected at pH 5.8 (for PEPT1) and pH 6.5 (for PEPT2), suggesting that both HeLa-hPEPT1 and HeLa-hPEPT2 were H(+) dependent transporters. Stably transfected HeLa-hPEPT1/HeLa-hPEPT2 cells were constructed successfully, and the functions of hPEPT1/hPEPT2 were identified using their substrates, JBP485 and Gly-Sar. The transfected cells with transporters were used to investigate drug-drug interactions (DDIs) between JBP485 and other substrates (cephalexin or lisinopril) of PEPT1 and PEPT2.

Responses of human endothelial cells to pathogenic and non-pathogenic Leptospira species

Leptospirosis is a widespread zoonotic infection that primarily affects residents of tropical regions, but causes infections in animals and humans in temperate regions as well. The agents of leptospirosis comprise several members of the genus Leptospira, which also includes non-pathogenic, saprophytic species. Leptospirosis can vary in severity from a mild, non-specific illness to severe disease that includes multi-organ failure and widespread endothelial damage and hemorrhage. To begin to investigate how pathogenic leptospires affect endothelial cells, we compared the responses of two endothelial cell lines to infection by pathogenic versus non-pathogenic leptospires. Microarray analyses suggested that pathogenic L. interrogans and non-pathogenic L. biflexa triggered changes in expression of genes whose products are involved in cellular architecture and interactions with the matrix, but that the changes were in opposite directions, with infection by L. biflexa primarily predicted to increase or maintain cell layer integrity, while L. interrogans lead primarily to changes predicted to disrupt cell layer integrity. Neither bacterial strain caused necrosis or apoptosis of the cells even after prolonged incubation. The pathogenic L. interrogans, however, did result in significant disruption of endothelial cell layers as assessed by microscopy and the ability of the bacteria to cross the cell layers. This disruption of endothelial layer integrity was abrogated by addition of the endothelial protective drug lisinopril at physiologically relevant concentrations. These results suggest that, through adhesion of L. interrogans to endothelial cells, the bacteria may disrupt endothelial barrier function, promoting dissemination of the bacteria and contributing to severe disease manifestations. In addition, supplementing antibiotic therapy with lisinopril or derivatives with endothelial protective activities may decrease the severity of leptospirosis.

Prevention of salt induced hypertension and fibrosis by angiotensin converting enzyme inhibitors in Dahl S rats

BACKGROUND AND PURPOSE

In Dahl S rats, high salt increases activity of the tissue renin-angiotensin-aldosterone system (RAAS) in the CNS, heart and kidneys. Here, we assessed the effects of chronic angiotensin converting enzyme (ACE) inhibition on salt-induced hypertension and cardiovascular and renal hypertrophy and fibrosis, relative to the extent of ACE blockade.

EXPERIMENTAL APPROACH

From 4.5 weeks of age, Dahl S rats received either the lipophilic ACE inhibitor trandolapril (1 or 5 mg kg(-1) day(-1)) or the hydrophilic ACE inhibitor lisinopril (10 or 50 mg kg(-1) day(-1)) and a high salt diet was started 0.5 week later. Treatments ended at 9 weeks of age.

KEY RESULTS

High salt diet markedly increased blood pressure (BP), decreased plasma angiotensin II and increased ACE binding densities in brain, heart, aorta and kidneys. Trandolapril and lisinopril prevented 50% of the increase in BP in light and dark period of the day. After the last doses, trandolapril decreased ACE densities by approximately 80% in brain nuclei and heart and lisinopril by approximately 60% in the brain and by approximately 70% in the heart. The two ACE inhibitors prevented right ventricular hypertrophy and attenuated left ventricular hypertrophy but did not affect renal hypertrophy caused by high salt. Both drugs prevented high salt-induced fibrosis in heart, kidney and aorta.

CONCLUSION AND IMPLICATION

As the ACE inhibitors could completely prevent tissue fibrosis and partially prevent tissue hypertrophy and hypertension, the tissue RAAS may play a critical role in salt-induced fibrosis, but a lesser role in the hypertrophy.

The role and regulation of cardiac angiotensin-converting enzyme for noninvasive molecular imaging in heart failure

Congestive heart failure is a pathologic condition characterized by progressive decrease in left ventricular contractility and consequent decline of cardiac output. There is convincing clinical and experimental evidence that the renin-angiotensin system (RAS) and its primary effector peptide, angiotensin II, are linked to the pathophysiology of interstitial fibrosis, cardiac remodeling, and heart failure. In addition to the traditional endocrine or circulating RAS, an active tissue RAS has been characterized. Tissue angiotensin-converting enzyme and locally synthesized angiotensin II, for example, by chymase, exert local trophic effects that modulate gene expression, which regulates growth and proliferation in both myocytes and nonmyocytes. The existence of the tissue RAS offers an opportunity for targeted imaging, which may be of considerable value for guiding medical therapy.

Inhibitory antibodies to human angiotensin-converting enzyme: fine epitope mapping and mechanism of action

Angiotensin I-converting enzyme (ACE), a key enzyme in cardiovascular pathophysiology, consists of two homologous domains (N and C), each bearing a Zn-dependent active site. We modeled the 3D-structure of the ACE N-domain using known structures of the C-domain of human ACE and the ACE homologue, ACE2, as templates. Two monoclonal antibodies (mAb), 3A5 and i2H5, developed against the human N-domain of ACE, demonstrated anticatalytic activity. N-domain modeling and mutagenesis of 21 amino acid residues allowed us to define the epitopes for these mAbs. Their epitopes partially overlap: amino acid residues K407, E403, Y521, E522, G523, P524, D529 are present in both epitopes. Mutation of 4 amino acid residues within the 3A5 epitope, N203E, R550A, D558L, and K557Q, increased the apparent binding of mAb 3A5 with the mutated N-domain 3-fold in plate precipitation assay, but abolished the inhibitory potency of this mAb. Moreover, mutation D558L dramatically decreased 3A5-induced ACE shedding from the surface of CHO cells expressing human somatic ACE. The inhibition of N-domain activity by mAbs 3A5 and i2H5 obeys similar kinetics. Both mAbs can bind to the free enzyme and enzyme-substrate complex, forming E.mAb and E.S.mAb complexes, respectively; however, only complex E.S can form a product. Kinetic analysis indicates that both mAbs bind better with the ACE N-domain in the presence of a substrate, which, in turn, implies that binding of a substrate causes conformational adjustments in the N-domain structure. Independent experiments with ELISA demonstrated better binding of mAbs 3A5 and i2H5 in the presence of the inhibitor lisinopril as well. This effect can be attributed to better binding of both mAbs with the "closed" conformation of ACE, therefore, disturbing the hinge-bending movement of the enzyme, which is necessary for catalysis.

Kinetic probes for inter-domain co-operation in human somatic angiotensin-converting enzyme

s-ACE (the somatic form of angiotensin-converting enzyme) consists of two homologous domains (N- and C-domains), each bearing a catalytic site. Negative co-operativity between the two domains has been demonstrated for cow and pig ACEs. However, for the human enzyme there are conflicting reports in the literature: some suggest possible negative co-operativity between the domains, whereas others indicate independent functions of the domains within s-ACE. We demonstrate here that a 1:1 stoichiometry for the binding of the common ACE inhibitors, captopril and lisinopril, to human s-ACE is enough to abolish enzymatic activity towards FA {N-[3-(2-furyl)acryloyl]}-Phe-GlyGly, Cbz (benzyloxycarbonyl)-Phe-His-Leu or Hip (N-benzoylglycyl)-His-Leu. The kinetic parameters for the hydrolysis of seven tripeptide substrates by human s-ACE appeared to represent average values for parameters obtained for the individual N- and C-domains. Kinetic analysis of the simultaneous hydrolysis of two substrates, Hip-His-Leu (S1) and Cbz-Phe-His-Leu (S2), with a common product (His-Leu) by s-ACE at different values for the ratio of the initial concentrations of these substrates (i.e. sigma=[S2]0/[S1]0) demonstrated competition of these substrates for binding to the s-ACE molecule, i.e. binding of a substrate at one active site makes the other site unavailable for either the same or a different substrate. Thus the two domains within human s-ACE exhibit strong negative co-operativity upon binding of common inhibitors and in the hydrolysis reactions of tripeptide substrates.

Development and validation of a stability indicating HPLC method for determination of lisinopril, lisinopril degradation product and parabens in the lisinopril extemporaneous formulation

The purpose of the research described herein was to develop and validate a stability-indicating HPLC method for lisinopril, lisinopril degradation product (DKP), methyl paraben and propyl paraben in a lisinopril extemporaneous formulation. The method developed in this report is selective for the components listed above, in the presence of the complex and chromatographically rich matrix presented by the Bicitra and Ora-Sweet SF formulation diluents. The method was also shown to have adequate sensitivity with a detection limit of 0.0075 microg/mL (0.03% of lisinopril method concentration). The validation elements investigated showed that the method has acceptable specificity, recovery, linearity, solution stability, and method precision. Acceptable robustness indicates that the assay method remains unaffected by small but deliberate variations, which are described in ICH Q2A and Q2B guidelines.

A calorimetric study of the binding of lisinopril, enalaprilat and captopril to angiotensin-converting enzyme

The angiotensin I-converting enzyme (ACE; EC.3.4.15.1) is a dipeptidyl carboxypeptidase that plays a central role in blood pressure regulation. The somatic form of the enzyme is composed of two highly similar domains, usually referred to as N and C domains, each containing one active site. Nevertheless, a 1:1 stoichiometry for the binding of lisinopril, captopril or enalaprilat to somatic pig lung ACE is shown by isothermal titration calorimetry (ITC) and enzymatic assays. The binding of the three inhibitors at neutral pH is very tight and the enthalpy changes are positive, indicating that the binding is entropically driven. The origin of this thermodynamic signature is discussed under the new structural information available.

Structural Determinants of RXPA380, a Potent and Highly Selective Inhibitor of the Angiotensin-Converting Enzyme C-Domain

RXPA380 (Cbz-PhePsi[PO(2)CH]Pro-Trp-OH) was reported recently as the first highly selective inhibitor of the C-domain of somatic angiotensin-converting enzyme (ACE), able to differentiate the two active sites of somatic ACE by a selectivity factor of more than 3 orders of magnitude. The contribution of each RXPA380 residue toward this remarkable selectivity was evaluated by studying several analogues of RXPA380. This analysis revealed that both pseudo-proline and tryptophan residues in the P(1)' and P(2)' positions of RXPA380 play a critical role in the selectivity of this inhibitor for the C-domain. This selectivity is not due to a preference of the C-domain for inhibitors bearing pseudo-proline and tryptophan residues, but rather reflects the poor accommodation of these inhibitor residues by the N-domain. A model of RXPA380 in complex with the ACE C-domain, based on the crystal structure of germinal ACE, highlights residues that may contribute to RXPA380 selectivity. From this model, striking differences between the N- and C-domains of ACE are observed for residues defining the S(2)' pocket. Of the twelve residues that surround the tryptophan side chain of RXPA380 in the C-domain, five are different in the N-domain. These differences in the S(2)' composition between the N- and C-domains are suggested to contribute to RXPA380 selectivity. The structural insights provided by this study should enhance understanding of the factors controlling the selectivity of the two domains of somatic ACE and allow the design of new selective ACE inhibitors.

Purified angiotensin converting enzyme from Rana esculenta ovary influences ovarian steroidogenesis in vitro

The aim of the present study was to purify and characterize angiotensin-converting enzyme (ACE) present in frog ovary (Rana esculenta). Detergent and trypsin-extracted enzymes were purified using a one-step process, consisting of affinity chromatography on lisinopril coupled to Sepharose 6B. The molecular mass was 150 kDa for both detergent-extracted and trypsin-extracted enzyme. The specific activity of detergent-extracted and trypsin-extracted ACE was 294 U mg(-1) and 326 U mg(-1) respectively. The optimum pH range was from 7-8.5 at 37 degrees C and the optimum temperature was 50 degrees C. Optimum chloride concentration was about 200 mM for synthetic substrate FAPGG (N-[3-(2-furyl)acryloyl] L-phenylalanyl glycyl glycine) and angiotensin I, and 10 mM for bradykinin. The Km and Kcat values for FAPGG were 0.608 +/- 0.07 mM and 249 sec(-1) respectively and I50 values for captopril and lisinopril, two specific ACE inhibitors, were 68 +/- 12.55 nM and 6.763 +/- 0.66 nM respectively. Frog ovary tissue from prereproductive period was incubated in vitro in the presence of frog ovary ACE (2.5 mU/ml), captopril (0.1 mM), and lisinopril (0.1 mM). Production of 17beta-estradiol, progesterone, and prostaglandins E2 and F2alpha was determined. The data showed a modulation of 17beta-estradiol, progesterone and prostaglandin E2 production by ovary ACE.

Structural basis of the lisinopril-binding specificity in N- and C-domains of human somatic ACE

Angiotensin I-converting enzyme (ACE) is a dipeptidyl carboxypeptidase which converts angiotensin I into the vasopressor peptide angiotensin II and also inactivates the hypotensive peptide bradykinin, playing an important role in blood pressure regulation. The present work describes the molecular modeling of the N-terminal human somatic ACE in complex with the inhibitor lisinopril, identifying the residues involved in the inhibitor-binding pocket. The obtained results identify differences in the lisinopril lysine moiety-binding residues for N- and C-terminals of sACE domains and an important carboxy-terminal proline hydrophobic accommodations mediated by the aromatic ring of Tyr532 and Tyr1128 residues, respectively. The present model will be useful for the development of a new inhibitor family based on the natural BPP peptides and derivatives, or even to improve the binding capacities and the domain specificity of the already known inhibitors.

Crystal structure of Drosophila angiotensin I-converting enzyme bound to captopril and lisinopril

Angiotensin I-converting enzymes (ACEs) are zinc metallopeptidases that cleave carboxy-terminal dipeptides from short peptide hormones. We have determined the crystal structures of AnCE, a Drosophila homolog of ACE, with and without bound inhibitors to 2.4 A resolution. AnCE contains a large internal channel encompassing the entire protein molecule. This substrate-binding channel is composed of two chambers, reminiscent of a peanut shell. The inhibitor and zinc-binding sites are located in the narrow bottleneck connecting the two chambers. The substrate and inhibitor specificity of AnCE appears to be determined by extensive hydrogen-bonding networks and ionic interactions in the active site channel. The catalytically important zinc ion is coordinated by the conserved Glu395 and histidine residues from a HExxH motif.

Crystal structure of the human angiotensin-converting enzyme-lisinopril complex

Angiotensin-converting enzyme (ACE) has a critical role in cardiovascular function by cleaving the carboxy terminal His-Leu dipeptide from angiotensin I to produce a potent vasopressor octapeptide, angiotensin II. Inhibitors of ACE are a first line of therapy for hypertension, heart failure, myocardial infarction and diabetic nephropathy. Notably, these inhibitors were developed without knowledge of the structure of human ACE, but were instead designed on the basis of an assumed mechanistic homology with carboxypeptidase A. Here we present the X-ray structure of human testicular ACE and its complex with one of the most widely used inhibitors, lisinopril (N2-[(S)-1-carboxy-3-phenylpropyl]-L-lysyl-L-proline; also known as Prinivil or Zestril), at 2.0 A resolution. Analysis of the three-dimensional structure of ACE shows that it bears little similarity to that of carboxypeptidase A, but instead resembles neurolysin and Pyrococcus furiosus carboxypeptidase--zinc metallopeptidases with no detectable sequence similarity to ACE. The structure provides an opportunity to design domain-selective ACE inhibitors that may exhibit new pharmacological profiles.

Fluorescence polarization studies of different forms of angiotensin-converting enzyme

The interaction of three forms of bovine angiotensin-converting enzyme (ACE) with the competitive peptide inhibitor lisinopril with a fluorescent label was studied using fluorescence polarization. The dissociation constants Kd of the enzyme-inhibitor complexes in 50 mM Hepes-buffer (pH 7.5) containing 150 mM NaCl and 1 microM ZnCl2 at 37 degrees C were (2.3 +/- 0.4).10(-8), (2.1 +/- 0.3).10(-8), and (2.1 +/- 0.2).10(-8) M for two-domain somatic ACE, single-domain testicular ACE, and for the N-domain of the enzyme, respectively. The interaction of the enzyme with the inhibitor strongly depended on the presence of chloride in the medium, and the apparent dissociation constant of the ACE-chloride complex was (1.3 +/- 0.2).10(-3) M for the somatic enzyme. The dissociation kinetics of the complex of the inhibitor with somatic ACE did not fit the kinetics of a first-order reaction, but it was approximated by a model of simultaneous dissociation of two complexes with the dissociation rate constants (0.13 +/- 0.01) sec(-1) and (0.026 +/- 0.001) sec(-1) that were present at approximately equal initial concentrations. The dissociation kinetics of the single-domain ACE complexes with the inhibitor were apparently first-order, and the dissociation rate constants were similar: (0.055 +/- 0.001) and (0.041 +/- 0.001) sec(-1) for the N-domain and for testicular ACE, respectively.

Characterization of bovine atrial angiotensin-converting enzyme

Bovine atrial angiotensin-converting enzyme (ACE) was purified to electrophoretic homogeneity. The purification procedure included ion-exchange chromatography on DEAE-Toyopearl 650M, affinity chromatography on lisinopril-agarose and gel filtration on Sephadex G-100. The bovine atrial ACE exhibited similar sensitivities to inhibition by lisinopril and captopril as lung ACE (the Ki values for the atrial and lung enzymes differed insignificantly). However, the kinetic parameters of hydrolysis of some synthetic tripeptide substrates (FA-Phe-Gly-Gly, FA-Phe-Phe-Arg, Cbz-Phe-His-Leu, Hip-His-Leu) catalyzed by bovine atrial and lung ACE varied to a greater extent. The enzymes were also characterized by some differences in activation by chloride, nitrate, and sulfate anions. These data support the hypothesis of tissue specificity of ACEs.

Angiotensin I-converting enzyme transition state stabilization by HIS1089: evidence for a catalytic mechanism distinct from other gluzincin metalloproteinases

Angiotensin (Ang) I-converting enzyme (ACE) is a member of the gluzincin family of zinc metalloproteinases that contains two homologous catalytic domains. Both the N- and C-terminal domains are peptidyl-dipeptidases that catalyze Ang II formation and bradykinin degradation. Multiple sequence alignment was used to predict His(1089) as the catalytic residue in human ACE C-domain that, by analogy with the prototypical gluzincin, thermolysin, stabilizes the scissile carbonyl bond through a hydrogen bond during transition state binding. Site-directed mutagenesis was used to change His(1089) to Ala or Leu. At pH 7.5, with Ang I as substrate, k(cat)/K(m) values for these Ala and Leu mutants were 430 and 4,000-fold lower, respectively, compared with wild-type enzyme and were mainly due to a decrease in catalytic rate (k(cat)) with minor effects on ground state substrate binding (K(m)). A 120,000-fold decrease in the binding of lisinopril, a proposed transition state mimic, was also observed with the His(1089) --> Ala mutation. ACE C-domain-dependent cleavage of AcAFAA showed a pH optimum of 8.2. H1089A has a pH optimum of 5.5 with no pH dependence of its catalytic activity in the range 6.5-10.5, indicating that the His(1089) side chain allows ACE to function as an alkaline peptidyl-dipeptidase. Since transition state mutants of other gluzincins show pH optima shifts toward the alkaline, this effect of His(1089) on the ACE pH optimum and its ability to influence transition state binding of the sulfhydryl inhibitor captopril indicate that the catalytic mechanism of ACE is distinct from that of other gluzincins.

Angiotensin-converting enzyme inhibition by lisinopril enhances liver regeneration in rats

Bradykinin has been reported to act as a growth factor for fibroblasts, mesangial cells and keratinocytes. Recently, we reported that bradykinin augments liver regeneration after partial hepatectomy in rats. Angiotensin-converting enzyme (ACE) is also a powerful bradykinin-degrading enzyme. We have investigated the effect of ACE inhibition by lisinopril on liver regeneration after partial hepatectomy. Adult male Wistar rats underwent 70% partial hepatectomy (PH). The animals received lisinopril at a dose of 1 mg kg body weight(-1) day(-1), or saline solution, intraperitoneally, for 5 days before hepatectomy, and daily after surgery. Four to six animals from the lisinopril and saline groups were sacrificed at 12, 24, 36, 48, 72, and 120 h after PH. Liver regeneration was evaluated by immunohistochemical staining for proliferating cell nuclear antigen using the PC-10 monoclonal antibody. The value for the lisinopril-treated group was three-fold above the corresponding control at 12 h after PH (P<0.001), remaining elevated at approximately two-fold above control values at 24, 36, 48 (P<0.001), and at 72 h (P<0.01) after PH, but values did not reach statistical difference at 120 h after PH. Plasma ACE activity measured by radioenzymatic assay was significantly higher in the saline group than in the lisinopril-treated group (P<0.001), with 81% ACE inhibition. The present study shows that plasma ACE inhibition enhances liver regeneration after PH in rats. Since it was reported that bradykinin also augments liver regeneration after PH, this may explain the liver growth stimulating effect of ACE inhibitors.

Isolation of angiotensin converting enzyme (ACE) binding protein from human serum with an ACE affinity column

Immobilized angiotensin-converting enzyme (ACE) was utilized as an affinity ligand to isolate a naturally occurring ACE binding protein from normal human serum. The enzyme was isolated from solubilized bovine lung membrane preparations by lisinopril affinity chromatography. It had an estimated molecular weight of 180 000 and was recognized by the anti-ACE antibody for the rabbit testicular ACE in immunoblots. ACE was immobilized onto epoxy Sepharose as well as Affi-Gel 15. Immobilized ACE on Affi-Gel 15 had higher catalytic activity (0.176 U/mL) compared with the enzyme immobilized on epoxy Sepharose (0.00005 U/mL). Immobilized ACE served as the affinity ligand for the identification of the ACE binding protein in human serum with an estimated molecular weight of 14 000 as observed by SDS polyacrylamide gel electrophoresis. The identification and further characterization of ACE binding proteins in serum and tissues may facilitate the greater understanding of the endogenous regulation of this key enzyme, which is involved in blood pressure homeostasis.

Presence and comparison of angiotensin converting enzyme in commercial cell culture sera

This study was conducted to determine the presence of the angiotensin converting enzyme in commercial sera used in cell culture medium. The aim of the research was to bring the presence of proteinases (angiotensin converting enzyme) to cell culture users' knowledge and to give some data for solving problems about the development of peptides as useful drugs. The enzymes, purified from foetal bovine, adult bovine, foetal equine, adult equine, and human sera, showed molecular weights of about 170 kDa. Captopril and lisinopril inhibited enzyme activities at nanomolar concentrations. The enzymes were able to hydrolyze, with different efficiency, angiotensin I, bradykinin and epidermal mitosis inhibiting pentapeptide. The heat inactivation of commercial sera at 56 degrees C for 30 min showed a reduction of ACE activity of about 35-80%. Therefore, the presence of ACE activity in commercial sera can influence the activity of biological peptides tested on cell lines cultured "in vitro."

Converting enzyme determines plasma clearance of angiotensin-(1-7)

We determined the mechanism accounting for the removal and metabolism of angiotensin-(1-7) [Ang-(1-7)] in 21 anesthetized spontaneously hypertensive (SHR), 18 age-matched normotensive Sprague-Dawley (SD), and 36 mRen-2 transgenic (TG+) rats. Animals of all 3 strains were provided with tap water or tap water containing losartan, lisinopril, or a combination of lisinopril and losartan for 2 weeks. On the day of the experiment, Ang-(1-7) was infused for a period of 15 minutes at a rate of 278 nmol . kg-1 . min-1. After this time, samples of arterial blood were collected rapidly at regular intervals for the assay of plasma Ang-(1-7) levels by radioimmunoassay. Infusion of Ang-(1-7) had a minimal effect on vehicle-treated SD rats but elicited a biphasic pressor/depressor response in vehicle-treated SHR and TG+ rats. In lisinopril-treated rats, Ang-(1-7) infusion increased blood pressure, whereas losartan treatment abolished the pressor component of the response without altering the secondary fall in arterial pressure. Combined treatment with lisinopril and losartan abolished the cardiovascular response to Ang-(1-7) in all 3 strains. In vehicle-treated SD, SHR and TG+ the half-life (t1/2) of Ang-(1-7) averaged 10+/-1, 10+/-1, and 9+/-1 seconds, respectively. Lisinopril alone or in combination with losartan produced a statistically significant rise in the half-life of Ang-(1-7) in all 3 strains of rats. Plasma clearance of Ang-(1-7) was significantly greater in the untreated SD rats compared with either the SHR or TG+ rat. Lisinopril treatment was associated with reduced clearance of Ang-(1-7) in all 3 strains. Concurrent experiments in pulmonary membranes from SD and SHR showed a statistically significant inhibition of 125I-Ang-(1-7) metabolism in the presence of lisinopril. These studies showed for the first time that the very short half-life of Ang-(1-7) in the circulation is primarily accounted for peptide metabolism by ACE. These findings suggest a novel role of ACE in the regulation of the production and metabolism of the two primary active hormones of the renin angiotensin system.

Calorimetric analysis of lisinopril binding to angiotensin I-converting enzyme

Isothermal titration microcalorimetry has been used to measure changes in enthalpy and heat capacity for binding of lisinopril to the angiotensin I-converting enzyme (ACE; EC 3.4.15.1) and to its apoenzyme at pH 7.5 over a temperature range of 15-30 degrees C. Calorimetric measurements indicate that lisinopril binds to two sites in the monomer of both holo- and apo-ACE. Binding of lisinopril to both systems is enthalpically unfavorable and, thus, is dominated by a large positive entropy change. The enthalpy change of binding is strongly temperature-dependent for both holo- and apo-ACE, arising from a large heat capacity change of binding equal to -2.4 +/- 0.2 kJ/K/mol of monomeric holo-ACE) and to -1.9 +/- 0.2 kJ/K/mol of monomeric apo-ACE), respectively. The negative values of deltaCp for both systems are consistent with burial of a large non-polar surface area upon binding. Although the binding of lisinopril to holo- and apo-ACE is favored by entropy changes, this is more positive for the holoenzyme. Thus, the interaction between Zn2+ and lisinopril results in a higher affinity of the holoenzyme for this drug due to a more favorable entropic contribution.

Inhibition of angiotensin converting enzyme from sheep tissues by captopril, lisinopril and enalapril

Inhibition of angiotensin converting enzyme(EC 3.4,15.1, ACE) in presence of captopril, lisinopril and enalapril were investigated in kidney, lung and serum of sheep using Hip-His-Leu(HHL) as substrate. The activity in kidney, lung and serum was inhibited at HHL concentration above 5 mM. The inhibitory constants (IC50) ranged between 5.6 nM for serum ACE with lisinopril and 70000 nM for renal ACE with enalapril while Ki ranged from 1.0 nM for serum ACE with lisinopril to 12000 nM for kidney ACE with enalapril. Differences in inhibition observed in different tissues suggest that the inhibitors may block function(s) of ACE to varying degrees in each tissue.

Molecular mechanism for the relative binding affinity to the intestinal peptide carrier. Comparison of three ACE-inhibitors: enalapril, enalaprilat, and lisinopril

The affinity of three substrates for the intestinal peptide carrier is explained based on their three-dimensional (3D) structural data. The kinetic transport parameters of three ACE-inhibitors, enalapril, enalaprilat, and lisinopril, have been determined in an in vivo system using rat intestine. The observed kinetic transport parameters (+/- asymptotic standard error) of enalapril are: 0.81 (+/- 0.23) mM, 0.58 (+/- 0.37) mumol/h per cm2, and 0.56 (+/- 0.04) cm/h for the half-maximal transport concentration (KT), the maximal transport flux (Jmax) and the passive permeability constant (Pm). Enalaprilat was transported by passive diffusional with a Pm of 0.51 (+/- 0.04) cm/h. For lisinopril the kinetic transport parameters were 0.38 (+/- 0.19) mM, 0.12 (+/- 0.07) mumol/h per cm2, and 0.18 (+/- 0.02) cm/h for KT, Jmax, and Pm, respectively. The affinity of the ACE-inhibitors for the intestinal peptide carrier has been evaluated based on their ability to inhibit the transport rate of cephalexin. The inhibition constants (Ki) of enalapril, enalaprilat and lisinopril were 0.15, 0.28 and 0.39 mM, respectively. 3D structural analysis of lisinopril using molecular modelling techniques reveals that intramolecular hydrogen bond formation is responsible for decreased carrier affinity.

Stability and in vitro absorption of captopril, enalapril and lisinopril across the rat intestine

In vitro absorption of three angiotensin converting enzyme (ACE) inhibitors, captopril, enalapril and lisinopril, and their stabilities in aqueous buffer as well as their resistance to intestinal and dermal tissue homogenates were investigated. The results demonstrate that the spontaneous oxidation of captopril, enalapril and lisinopril followed first-order degradation kinetics in McIlvaine's citrate-phosphate buffer. The degradation rates for enalapril and lisinopril were much slower than that for captopril. With the former two ACE inhibitors, the first-order rate constants of breakdown in the presence of dermal homogenate were not significantly different from the control values. Intestinal homogenate increased the decomposition of both of these inhibitors when compared to the enzyme-free control systems. On the other hand, the first-order rates of disappearance of captopril in the presence of both dermal and intestinal homogenates were lower than in the enzyme-free system. The extent of reduction was proportional to the amount of homogenate added. This suggests that tissue homogenates prevent the oxidation of captopril to its disulphide dimer. Transport experiments show that the amounts of ACE inhibitors transferred from solution on the mucosal side increased linearly with incubation time over the 2 hr of study. The rates of transfer from the mucosal side to the serosal side had the following rank order: captopril > enalapril > lisinopril roughly in the ratio 1:1.13:1.27. Addition of harmaline caused a significant reduction in the transfer rate of captopril compared to the control system, which strongly suggests that captopril is transported by a sodium-dependent carrier-mediated process across intestinal tissue.

Structural constraints of inhibitors for binding at two active sites on somatic angiotensin converting enzyme

Angiotensin converting enzyme active sites from rat plasma, lung, kidney and testis were assessed by comparative radioligand binding studies under physiological chloride conditions. Displacement of [125I]Ro 31-8472 from somatic and plasma angiotensin converting enzyme by angiotensin converting enzyme inhibitors of different structure indicated two binding sites (perindoprilat: high affinity carboxyl site, KDC 18 +/- 6 pM), and a single high affinity binding site on testis angiotensin converting enzyme (KDC 20 +/- 1 pM). Displacement of [125I]351A from plasma, somatic and testis angiotensin converting enzyme occurred at a single high affinity binding site. Reduction in affinity at the amino binding site of somatic angiotensin converting enzyme was related to an increased side chain size (lung KDA (pM): Ro 31-8472 175 +/- 38, lisinopril 2205 +/- 1832, and 351A 2271 +/- 489), or hydrophobicity of the competing unlabelled angiotensin converting enzyme inhibitor (lung KDA (pM): quinaprilat 1267 +/- 629 and perindoprilat 824 +/- 6). This trend was reversed at the carboxyl binding site of plasma, somatic and testis angiotensin converting enzyme. Bradykinin hydrolysis by lung angiotensin converting enzyme was inhibited in a similar manner by cilazaprilat or quinaprilat (F = 0.64, F-test based on the extra sum-of-squares principle; P > 0.05), indicating the angiotensin converting enzyme carboxyl active site predominates in bradykinin cleavage. The data demonstrate that the two binding sites on native plasma and somatic angiotensin converting enzyme are of potentially different functional and structural nature, suggesting they may have different substrate specificities.

Mutations in two specific residues of testicular angiotensin-converting enzyme change its catalytic properties

Chemical modifications of 2 specific residues present in angiotensin-converting enzyme (ACE) result in its inactivation, thereby suggesting that these 2 residues may be important for its enzyme activity. We directly tested this hypothesis by substituting Tyr-236 with Phe and Lys-154 with Glu in rabbit testicular ACE (ACET) using site-directed mutagenesis of the corresponding cDNA. Wild type ACET, the two single mutants, and the double mutant were expressed in HeLa cells using the vaccinia virus-T7 polymerase expression system. The rate of synthesis, post-translational modifications, and cleavage secretion pattern of all four proteins were indistinguishable. The enzymatic properties of the two single mutants and the wild type enzyme were also very similar. In contrast, the double mutant had about a 20-fold lower specific activity although its Km was only 6-fold higher than that of the wild type protein. The double mutant also had a 100-fold higher Ki for lisinopril, a competitive inhibitor of ACET, and was 17-fold less sensitive to stimulation by NaCl, an activator of ACET. These results directly demonstrate that Tyr-236 and Lys-154 are indeed critical for the catalytic activity, lisinopril inhibition, and NaCl activation of ACET.

Angiotensin-converting enzyme and myocardial fibrosis in the rat receiving angiotensin II or aldosterone

Angiotensin-converting enzyme (ACE) is present in tissues composed largely of fibrillar collagen such as heart valves, the adventitia of great vessels and intramyocardial coronary arteries, and the scar that follows myocardial infarction. We tested the hypothesis that such tissue ACE is related to fibrous tissue formation and that its appearance is independent of circulating renin and angiotensin peptides. For this purpose we selected experimental models that simulate primary and secondary hyperaldosteronism, each of which are associated with the appearance of myocardial fibrosis. ACE in the excised heart and aorta was localized by in vitro autoradiography with [125I]351A, while fibrosis was identified by light microscopy in sections stained with collagen specific picrosirius red. Tissue was obtained at 2, 4, and 6 weeks from various experimental groups: unoperated, untreated, age- and sex-matched controls; age- and sex-matched uninephrectomized control rats on a high sodium diet; and rats that had received either aldosterone (ALDO) or angiotensin II (AII). Compared with controls, we found ACE binding (1) unchanged after 2 weeks of ALDO, but increased in the adventitia of intramural coronary arteries after 4 weeks, in keeping with the perivascular fibrosis that appeared in each ventricle; (2) markedly increased after 6 weeks of ALDO, where it not only involved coronary vessels but also microscopic scars that appeared in atria and ventricles; (3) increased in the coronary adventitia and sites of scarring, each of which were present 2 weeks after AII; and (4) markedly increased after 4 and 6 weeks of AII as fibrosis became more extensive.(ABSTRACT TRUNCATED AT 250 WORDS)